Despite their relatively small geographic footprints, coral reefs are pivotal for ocean ecosystems. They support as much as 25% of marine life in the oceans. They’re also very sensitive to change. It’s one reason why coral reefs have been referred to as “canaries in the coal mine” for understanding ocean health.
When temperatures rise too much, coral reefs undergo a process known as bleaching. The algae that normally have a symbiotic relationship with the coral are expelled, weakening the coral and making them appear white, or bleached. Prolonged bleaching can kill coral and devastate ecosystems.
The good news is that coral bleaching is detectable and predictable. The National Oceanic and Atmospheric Administration’s (NOAA’s) Coral Reef Watch uses satellites to track sea surface temperatures around reefs. NOAA can flag alerts when temperatures rise above thresholds known to cause bleaching. This interactive map from Esri uses data from NOAA’s 213 virtual coral reef stations to monitor coral reefs at risk of bleaching.
The daily updated map serves as an interactive dashboard for coral reef health. You can immediately see how many of the 213 stations are at risk of bleaching. For this map, “at risk” refers to reefs that are under a Warning, Alert 1, or Alert 2.
Clicking an alert returns a filtered list of reef stations. You can also click on reefs and stations in the map to learn more about the current status of each. Both reefs and stations provide context about the current status of the reef in plain language. For example, a reef with an alert level 2 notes that “the area is likely experiencing coral mortality.”
In addition to alert level, stations also report sea surface temperature, temperature anomaly, hotspots, and degree heating weeks. It’s these data that determine the alert level for coral. The pop-up also includes a detailed graph of temperatures and thresholds at that station over time.
As they provide key support to marine ecosystems, coral reefs also protect shorelines from storms and drive ecotourism. Reefs can be restored, and they can also be protected during bleaching events. As ocean temperatures continue to rise, monitoring and protecting coral reefs will be critical for the ocean’s health. And our own.
More to Explore
- Learn more about how this interactive map was created.
- Get an overview of the importance of coral reefs.
- Discover how coral reefs can be protected from bleaching events.
- Take a deep dive into coral reef restoration.
